Contact allergy to formaldehyde

ORIGINAL ARTICLE, p 568 Formaldehyde is an important contact allergen in consumer products and in industry; 2–3% (Europe) to 8–9% (U.S.A.) of patients suspected of allergic contact dermatitis react to a patch test with this preservative. Patch testing with formaldehyde is problematic and the optimal test concentration has not been established. Formerly, test concentrations of 3–5% caused irritant reactions. In the 1980s, 2% was used; the current concentration of 1% in water was recommended by the International Contact Dermatitis Research Group. Because of a probable lack of scientific data behind this change, and also based on the impression that false‐negative results occur with the 1% concentration, two studies have previously compared the results of testing with 1% and 2% formaldehyde.1, 2 In the former study,1 no significant difference between the two test concentrations was found. More recently, 1397 patients with dermatitis were patch tested with 1% and 2% aqueous formaldehyde, using standardized amounts of 15 μL of the solutions applied with a micropipette to the filter paper discs in the test chambers (Finn Chamber).2 Sixty‐eight patients (4·9%) were found to have contact allergy to formaldehyde. Thirty‐seven of them reacted positively only to formaldehyde 2%, 29 patients reacted to both concentrations, and two reacted to the 1% concentration only. Thus, testing with 2% detected twice as many individuals with formaldehyde contact allergy.2